The present invention relates to loose-leaf binders and holders for loose filing sheets and in particular to a clasp element for holding sheets at two or more holes along a margin so that they are bound together firmly for ready use and referral as a document and which permits removing and/replacing sheets of the document from time to time.
Heretofore a common holder for loose-leaf pages that are punched with holes along one margin is the multiple ring loose-leaf folder which includes two or more rings (a ring for each hole in the margin of the pages) that are mechanically connected together so that the rings can be opened and closed together. The rings are of fixed diameter and attached together within a heavy folder and snap open and close together and so with such multiple ring loose-leaf folders it is relatively easy to load and unload pages in the folder. The typical multiple ring folder of this sort provides a document holder to which pages may be added and so the thickness of the document may increase until the rings are full and can hold no more pages. A disadvantage of this kind of holder is that the holder thickness is fixed and, as a result, whether it contains a few pages or many pages, it occupies the same space on a bookshelf. An advantage is that the folder can be laid flat on a table and opened to any page and, as opened, lays flat so that two consecutive pages are fully in view and lay flat for reading or referral. This feature is particularly desirable when the document contained in the loose-leaf folder is used in conjunction with plans, drawings, etc. and will lay flat at any page it is turned to and does not have to be held open by the user at the desired page. Another disadvantage of the multiple ring folder is that it is relatively expensive and is not usually used when providing many copies of a document that are used for a short time and then discarded after a few weeks or months, such as a document of building specifications.
Another type of binder that avoids some of these limitations and disadvantages of the multiple ring binder is the plastic binding element. Before binding with the plastic binding element, the sheets of the document are usually punched with a multitude of evenly spaced rectangular shaped holes along one margin. As binding, a great number of plastic rings are fed through these holes using a special tool. The plastic rings are usually individual rings all the same diameter and each is formed by two overlapping arms extending from a common spine. The special tool is used to insert the rings through the holes in the pages in the document and once so inserted, the rings are not easily removed and often require use of the tool, which may be the same tool or another tool, to remove the rings so that pages can be replaced or exchanged in the document and then the document is bound up again.
The diameter of the rings of the plastic binding element is usually selected in view of the thickness of the document and so if a number of pages are added to the document, a larger diameter plastic binding element must be used. An advantage gained using the plastic binding element is that the thickness of the document need be no greater than the thickness of the pages of the document. In other words the diameter of the plastic rings can be selected so that it is only slightly larger than the thickness of the document and it will serve adequately. Then, the document need occupy no more space on a shelf than dictated by its thickness.
Another advantage of the plastic binding element is that the document it binds may be open to any page and laid flat on a table and will remain open at the page. It shares this advantage with the multiple ring folder. A disadvantage is clearly that special tools must be used to insert and to open the plastic binding element to add or replace pages in the document.
Another type of loose-leaf binder is the post and holder type which may consist simply of individual screw posts, one for each hole along a margin of the sheets that are bound. In a more elaborate form the post and holder type binder includes folders, one for carrying the posts and the other for carrying the holders. In all of these, the posts enter the holes in a stack of sheets from one side and either emerge from the other side or are contacted therein by a holder from the other side. For the simple screw posts, the post is equipped to receive either a nut or screw that enters or contacts it from the other side of the stack of papers and so secures the papers together.
There are many forms of folders with posts and holders. Some are of adjustable thickness and others are of fixed thickness. One conventional post and holder type binder is known as the Acco binder that consists of two posts rising from a flat piece that enter the holes through a stack of sheets on one side of the stack and emerge from the other side. The holder is mounted to the emerging posts and slides over them to the thickness of the stack of sheets and then the portions of the posts beyond the holder are bent and secured. An advantage of the Acco type of post and holder binder is that it can be adjusted to the thickness of the document and it can be closed and opened without tools to remove and/replace sheets in the document. However, it is intrinsic with all post and holder type of binders that the document bound cannot be opened to any page and folded flat on a table. Furthermore, a relatively large margin must be left along the bound edge of the pages, because the document cannot be opened so as to fully expose a whole page. The post and holder binder prevents prevents this.